Characterization and sequence diversity of the Gsp-1 gene in diploid species of the Aegilops genus

Several studies have suggested a minor role in determining grain endosperm texture for the Gsp-1 gene, although appears related with the synthesis of the arabinogalactan-peptide. The current study evaluated the allelic variability of Gsp-1 genes in five diploid species of the Aegilops genus along with the molecular characterization of the main allelic variants found in each species and their phylogenetic relationships with the polyploid wheats. There was a high level of polymorphism in Gsp-1 genes – up to 19 alleles were obtained, of which 11 were novel. The processing of Gsp-1 amino acid sequences led to two main domains: AGP (arabinogalactan peptide) and GSP-1 (grain softness protein). Several substitutions were detected in both domains with respect to the bread wheat sequences, which could modify grain hardness. The sequences obtained showed relationship with the Gsp-B1 and Gsp-D1 genes of common wheat. These results showed that diploid Aegilops species are a rich resource of novel genetic variability for the Gsp-1 gene, whose hypothetical functionality should be tested in the genetic pool of modern wheat, valuing as the true role of these genes in grain hardness and their effective role as source of the AGP, a non-starch polysaccharide with health properties.     

The Gsp-1 genes encode the wheat arabinogalactan peptide

Western blotting, ELISA and ¹H-NMR spectroscopy showed that RNAi down-regulation of the wheat Gsp-1 gene resulted in reduced contents of both arabinogalactan peptide (AGP) and grain softness protein (GSP-1) in mature wheat grains confirming that these components are encoded by the same gene. A small increase in grain hardness and decrease in the viscosity of aqueous extracts of the transgenic lines also indicated small effects on functional properties. Immunolocalisation using a novel wheat AGP monoclonal antibody in conjunction with confocal microscopy showed that the major form of AGP which was eliminated in knockout lines is located within the cell, probably in the vacuole, and not in the plasma membrane or cell wall. However, clear localisation of the AGP epitope to the plasma membrane was observed in both control and transgenic lines and probably resulted from the presence of one or more separate forms of arabinogalactan protein. The existence of such additional form(s) was also indicated by ¹H-NMR spectroscopy which showed that the ratio of arabinose to galactose differed between the control and transgenic lines.     

Cloning and expression analysis of kenaf (Hibiscus cannabinus L.) major lignin and cellulose biosynthesis gene sequences and polymer quantification during plant development

In order to apply state-of-the-art molecular breeding techniques in fibre crop it is necessary to have a good knowledge of major polymer biosynthesis gene sequences and their expression pattern. Polymerase chain reaction was employed to isolate sequences of the major genes for lignin and cellulose biosynthesis in a kenaf cultivar. CeSA, 4cl, c4h, cad, and ccr gene primers were designed according to their conservative regions; partial sequences of lignin and cellulose biosynthesis genes were obtained. One actin II gene sequence was also isolated from the kenaf genome as a housekeeping gene to be employed in qPCR analysis. Expression levels of genes c4h, cad and CeSA in bark and core from plants harvested at three different growth stages were evaluated. Using qPCR analyses it was found that the expression levels of the two biosynthesis lignin genes in bark tissues increased during plant growth, while a negative trend was recorded in core tissues. In both bark and core, the quantity of lignin was positively correlated to plant growth while cellulose content decreased.     

Comparative Analysis of Glycoside Hydrolases Activities from Phylogenetically Diverse Marine Bacteria of the Genus Arenibacter

A total of 16 marine strains belonging to the genus Arenibacter, recovered from diverse microbial communities associated with various marine habitats and collected from different locations, were evaluated in degradation of natural polysaccharides and chromogenic glycosides. Most strains were affiliated with five recognized species, and some presented three new species within the genus Arenibacter. No strains contained enzymes depolymerizing polysaccharides, but synthesized a wide spectrum of glycosidases. Highly active β-N-acetylglucosaminidases and α-N-acetylgalactosaminidases were the main glycosidases for all Arenibacter. The genes, encoding two new members of glycoside hydrolyses (GH) families, 20 and 109, were isolated and characterized from the genomes of Arenibacter latericius. Molecular genetic analysis using glycosidase-specific primers shows the absence of GH27 and GH36 genes. A sequence comparison with functionally-characterized GH20 and GH109 enzymes shows that both sequences are closest to the enzymes of chitinolytic bacteria Vibrio furnissii and Cellulomonas fimi of marine and terrestrial origin, as well as human pathogen Elisabethkingia meningoseptica and simbionts Akkermansia muciniphila, gut and non-gut Bacteroides, respectively. These results revealed that the genus Arenibacter is a highly taxonomic diverse group of microorganisms, which can participate in degradation of natural polymers in marine environments depending on their niche and habitat adaptations. They are new prospective candidates for biotechnological applications due to their production of unique glycosidases.     

Occurrence and characterization of fungi and oomycetes transmitted via potting mixtures and organic manures

A study was conducted to investigate the most common fungal and oomycete pathogens introduced into farms in Oman via potting mixtures and organic manures. A total of 37 commercial types of potting mixtures (2 local and 35 imported from overseas), 4 commercial types of organic manures and 11 non-commercial types of organic manures were included in the study. Identification of the isolated species was based on morphological characteristics, except for the most common species which were further identified using sequences of the internal transcribed spacer region of the ribosomal DNA (ITS rDNA). Fusarium spp. (14%), Pythium aphanidermatum (3%), Alternaria spp. (5%), Helminthosporium spp. (5%) and Cladosporium spp. (3%) were recovered at different frequencies from samples of potting mixtures. Fusarium solani (40%) and Fusarium equiseti (47%) were recovered at high frequencies from samples of organic manures. Isolations from organic manures also yielded Pythium periplocum (7%), Rhizoctonia solani (7%), Fusarium lichenicola (7%), Helminthosporium spp. (27%) and Alternaria spp. (27%). Trichoderma spp., Penicillium spp., Aspergillus spp. and Rhizopus spp. were found to be common in samples of potting mixtures and organic manures. Investigating sensitivity to hymexazol among 9 isolates of F. equiseti and 13 isolates of F. solani revealed variations among different isolates. The EC₅₀ values ranged from 1 to over 1200 (avg. 192 μg ml⁻¹) for F. equiseti isolates and from 135 to 789 (avg. 324 μg ml⁻¹) for F. solani isolates, indicating presence of resistance to this important fungicide among some Fusarium isolates. This appears to be the first report of contamination with R. solani, P. periplocum, F. solani, F. equiseti and F. lichenicola of organic manures. This study appears to report for the first time F. lichenicola in Oman and appears to be the first report of occurrence of resistance to hymexazol among F. equiseti and F. solani isolates.     

Characterisation of a ω-gliadin gene in Triticum tauschii

A ω-gliadin gene at the Gli-D^t1 locus of Triticum tauschii accession AUS18913 was isolated using PCR primers, designed from published sequences of ω-gliadin genes of bread wheat cv Cheyenne, and deduced sequences of the N-terminal amino acids of ω-gliadin proteins. Further, the derived protein was isolated from A-PAGE and was sequenced. The protein sequence contained a signal peptide of 19 amino acids followed by a short N-terminal sequence of 11 amino acids, a central repetitive domain that covers approximately 90% of the sequence and a short C-terminal domain of 12 amino acids. The sequence comparison with other ω-gliadins showed a high level of similarities between them. Further analysis of the ω-gliadins using A-PAGE revealed that there are three ω-gliadin proteins in AUS18913 accession. Comparison of N-terminal sequences of these proteins revealed that two of these proteins have very high homologies with ω-gliadins of Cheyenne while the third one was significantly different.     

Puroindoline genes and proteins in tetraploid and hexaploid species of Triticum

Six tetraploid (5 Triticum turgidum and 1 Triticum timopheevii) and four hexaploid (three Triticum aestivum and one Triticum kiharae) taxa of Triticum were studied in order to identify novel variation in Pin genes and proteins which can be exploited in the improvement of cultivated wheat. Western blotting with a highly specific antibody showed that puroindoline proteins were present in all of the hexaploid lines but were absent from the tetraploids. The immunoreactive bands differed slightly in their relative mobilities and their relative amounts, which could have resulted from variation in the allelic forms of Pin a and Pin b. This was supported by HPLC analyses which showed differences in the retention times and peaks heights of the putative puroindoline components in T. kiharae and T. timopheevii. Sequence analyses of cDNAs also showed variation in the sequences of expressed puroindoline genes. In particular, a sequence encoding a new form of Pin b was present in T. aestivum ssp. macha.     

Gene Sequence Based Clustering Assists in Dereplication of Pseudoalteromonas luteoviolacea Strains with Identical Inhibitory Activity and Antibiotic Production

Some microbial species are chemically homogenous, and the same secondary metabolites are found in all strains. In contrast, we previously found that five strains of P. luteoviolacea were closely related by 16S rRNA gene sequence but produced two different antibiotic profiles. The purpose of the present study was to determine whether such bioactivity differences could be linked to genotypes allowing methods from phylogenetic analysis to aid in selection of strains for biodiscovery. Thirteen P. luteoviolacea strains divided into three chemotypes based on production of known antibiotics and four antibacterial profiles based on inhibition assays against Vibrio anguillarum and Staphylococcus aureus. To determine whether chemotype and inhibition profile are reflected by phylogenetic clustering we sequenced 16S rRNA, gyrB and recA genes. Clustering based on 16S rRNA gene sequences alone showed little correlation to chemotypes and inhibition profiles, while clustering based on concatenated 16S rRNA, gyrB, and recA gene sequences resulted in three clusters, two of which uniformly consisted of strains of identical chemotype and inhibition profile. A major time sink in natural products discovery is the effort spent rediscovering known compounds, and this study indicates that phylogeny clustering of bioactive species has the potential to be a useful dereplication tool in biodiscovery efforts.     

Natural Products from Antarctic Colonial Ascidians of the Genera Aplidium and Synoicum: Variability and Defensive Role

Ascidians have developed multiple defensive strategies mostly related to physical, nutritional or chemical properties of the tunic. One of such is chemical defense based on secondary metabolites. We analyzed a series of colonial Antarctic ascidians from deep-water collections belonging to the genera Aplidium and Synoicum to evaluate the incidence of organic deterrents and their variability. The ether fractions from 15 samples including specimens of the species A. falklandicum, A. fuegiense, A. meridianum, A. millari and S. adareanum were subjected to feeding assays towards two relevant sympatric predators: the starfish Odontaster validus, and the amphipod Cheirimedon femoratus. All samples revealed repellency. Nonetheless, some colonies concentrated defensive chemicals in internal body-regions rather than in the tunic. Four ascidian-derived meroterpenoids, rossinones B and the three derivatives 2,3-epoxy-rossinone B, 3-epi-rossinone B, 5,6-epoxy-rossinone B, and the indole alkaloids meridianins A–G, along with other minoritary meridianin compounds were isolated from several samples. Some purified metabolites were tested in feeding assays exhibiting potent unpalatabilities, thus revealing their role in predation avoidance. Ascidian extracts and purified compound-fractions were further assessed in antibacterial tests against a marine Antarctic bacterium. Only the meridianins showed inhibition activity, demonstrating a multifunctional defensive role. According to their occurrence in nature and within our colonial specimens, the possible origin of both types of metabolites is discussed.     

Antibodies to N-terminal Peptides of Low MrSubunits of Wheat Glutenin. II. Detection of Subunits Encoded by Different Loci

A panel of anti-peptide antibodies specific for each of the different N-terminal sequence types of B- and C-low molecular mass glutenin subunits (L M_rGS) were utilised in immunoblotting studies to identify the chromosomal location of genes encoding different sequences and to characterise the allelic variation of the encoding loci. The MET-type sequences were predominantly found among the B- subunits, while the α- and γ- sequences predominated in the C- subunits. The quantitatively major SHIPGLERPS sequence was found in both the B- and C- mobility regions. Using either biotypes in the cultivar, Aroona or genetic lines containing double rye chromosome 1 substitutions and thus expressing only single LM_r GS alleles, the sequences were determined for most of the major polypeptides expressed by each LM_r GS allele. The L M_rGS from different genomes encoded different numbers of each sequence type. Furthermore, different polypeptides within a particular «block» of subunits encoded by a given allele often had differing N-terminal sequences. However, subunits of similar electrophoretic mobilities encoded by different alleles at each locus usually had identical N-terminal sequences, suggesting that they may instead differ in the number of repeats. In Chinese Spring, genes encoding the SHIPGLERPS and METSHIPGL sequence types were predominantly present on chromosomes 1B and 1D, while the related METSRVPGL sequence was only encoded on 1D. In contrast, the METSCIPGL, α- and γ-sequences were encoded on each of chromosomes 1A, 1B and 1D. Several different electrophoretic and immunoblotting approaches using null lines suggested that some of the α-type L M_rGS may also be encoded by group 6 chromosomes, particularly 6D. The anti- SHIPGLERPS antibody also recognised chromosome 1B encoded β-, γ- and ω-gliadins, while the anti-METSRVPGL antibody recognised 1D encoded α- and β-gliadins. The absence of sequences within the major gliadin families that are highly homologous to the latter two N-terminal L M_rGS sequences may suggest that some monomeric L M_rGS could exist within the electrophoretically-resolved gliadins. These antibodies will provide valuable reagents for the study of the roles of particular L M_rGS families in the structure and function of the glutenin macropolymer, the role of different LM_r GS types in determining the influence of allelic variation of L M_rGS composition on dough properties, and potentially in the development of diagnostics for these flour components.     

Reduced height alleles (Rht) and Hagberg falling number of wheat

Near-isogenic lines varying for alleles for reduced height (Rht) and photoperiod insensitivity (Ppd-D1) in cv. Mercia (2005/6–2010/11; rht (tall), Rht-B1b, Rht-D1b, Rht-B1c, Rht8c+Ppd-D1a, Rht-D1c, Rht12) and cvs Maris Huntsman and Maris Widgeon (2007/8–2010/11; rht (tall), Rht-B1b, Rht-D1b, Rht-B1c, Rht-B1b+Rht-D1b, Rht-D1b+Rht-B1c) were compared at one field site, but within different systems (‘organic’, O, 2005/6–2007/8 v. ‘intensive’, I, 2005/6–2010/11). Further experiments at the site (2006/7–2008/9) compared 64 lines of a doubled-haploid (DH) population [Savannah (Rht-D1b) × Renesansa (Rht-8c+Ppd-D1a)]. Gibberellin (GA) insensitive dwarfing alleles (Rht-B1b; Rht-B1c; Rht-D1b; Rht-D1c) could reduce α-amylase activity and/or increase Hagberg falling number (HFN) but effects depended greatly on system, background and season. Only Rht-B1c increased grain dormancy despite producing plants taller than Rht-D1c. The GA-sensitive Rht8c+Ppd-D1a in Mercia was associated with reduced HFN but analysis of the DH population suggested this was more closely linked with Ppd-D1a, rather than Rht8c. The GA-sensitive severe-dwarfing allele Rht12 was associated with reduced HFN. Instability in HFN over season tended to increase with degree of dwarfing. There was a negative association between mean grain weight and HFN that was in addition to effects of Rht and Ppd-D1 allele.     

Genetic characterization of kernel polyphenol oxidases in wheat and related species

Polyphenol oxidase (PPO) activity causes undesirable darkening of raw Asian noodles and other wheat products. In this study we investigate the genetic origins and diversity of wheat kernel PPO. PPO was characterized via activity assays, antigenic staining, and Southern blots in Triticum aestivum, Triticum dicoccoides, Triticum durum, Triticum dicoccum, Triticum monococcum, Triticum urartu, Aegilops speltoides, and Aegilops tauschii. Among these species, PPO activity was well-correlated with antigenic staining intensity toward a wheat kernel-type PPO antibody. High PPO activity was observed in all three T. monococcum accessions (A^m genome), one Ae. speltoides accession, one T. durum accession, and two hexaploid wheat cultivars. Southern blots suggested the presence of two or more kernel-type PPO genes in diploid progenitors of the hexaploid A, B, and D genomes. Whole-kernel PPO activity was evaluated in disomic substitution lines derived from three T. dicoccoides accessions in the background of T. durum ‘Langdon’. PPO activity was primarily associated with chromosome 2A and to a much lower degree with chromosome 2B. DNA sequence comparisons showed that the intron associated with the high PPO allele on chromosome 2AL of hexaploid wheat had 94% nucleotide identity with the homeologous intron found in T. monococcum, a species with high kernel PPO activity. This implies that the ancestral PPO allele on the A genome is one of the high activity, and the low PPO allele found in hexaploid wheat represents a relatively recent genetic alteration. Results confirm the presence of multiple kernel-type PPO genes in the diploid and tetraploid progenitors and relatives of hexaploid wheat. However, it is likely that relatively few of the many kernel-type PPO genes present in wheat contribute substantially to kernel PPO activity. A single genetic locus on homeologous group 2 chromosomes may be the primary cause of high PPO activity in wheat kernels.     

Single versus multiple releases of predatory mites combined with spinosad for the management of western flower thrips in strawberry

Western flower thrips, Frankliniella occidentalis (Pergande), is a major pest of strawberry and other horticultural and ornamental crops. Biological control of F. occidentalis with predatory mites is recommended as an additional management strategy to chemical control in glasshouse and protected crops. However, it is not known whether multiple (two or three) species releases of predatory mites are more effective than single species releases. The effect of an application of spinosad followed by mite releases could further increase suppression of F. occidentalis. In a series of trials in the glasshouse, we evaluated three commercially available predatory mite species, Typhlodromips montdorensis (Schicha), Neoseiulus cucumeris (Oudemans) and Hypoaspis miles (Berlese). Strawberry plants were sprayed once with either spinosad at the recommended rate or with water. F. occidentalis adults were released onto plants 24 h after spraying, and mites were released six days later. Spinosad significantly reduced F. occidentalis compared to the control (water). T. montdorensis, N. cucumeris and H. miles significantly reduced F. occidentalis compared to the ‘no mite’ treatment. Spinosad had no effect on T. montdorensis and N. cucumeris, as their numbers did not differ between the spinosad and control treatments; H. miles was not recovered. When mites were released after an application of spinosad, greater suppression of F. occidentalis was achieved than with releases of predatory mites alone. When released as a double species combination, ‘T. montdorensis and H. miles’ was the most effective combination. There was no difference in efficacy between releases of ‘T. montdorensis and H. miles’ or ‘T. montdorensis, N. cucumeris and H. miles’. We conclude that multiple species releases are more effective than single species releases, and that biological control of F. occidentalis with predatory mites can be used together with spinosad.     

Development of STS markers and establishment of multiplex PCR for Glu-A3 alleles in common wheat (Triticum aestivum L.)

Low-molecular-weight glutenin subunits (LMW-GS) play a key role in determining the processing quality of the end-use products of common wheat. The objectives of this study were to identify genes at Glu-A3 locus, develop the STS markers, and establish multiplex PCR with the STS markers for Glu-A3 alleles. Gene-specific PCR primers were designed to amplify six near-isogenic lines (NILs) and Glenlea with different Glu-A3 alleles (a, b, c, d, e, f and g) defined by the protein electrophoretic mobility. Three Glu-A3 genes with complete coding sequence were cloned, designated as GluA3-1, GluA3-2 and GluA3-3, respectively. Seven dominant allele-specific STS (sequence tagged sites) markers were designed based on the SNPs (single nucleotide polymorphisms) among different allelic variants for the discrimination of the Glu-A3 protein alleles a, b, c, d, e, f and g. Four multiplex PCRs were established including Glu-A3b + Glu-A3f, Glu-A3d + Glu-A3f, Glu-A3d + Glu-A3g, and Glu-A3b + Glu-A3e. These markers and multiplex-PCR systems were validated on 141 CIMMYT wheat varieties and advanced lines with different Glu-A3 alleles, confirming that they can be efficiently used in marker-assisted breeding.     

Comparative susceptibility of Ostrinia furnacalis, Ostrinia nubilalis and Diatraea saccharalis (Lepidoptera: Crambidae) to Bacillus thuringiensis Cry1 toxins

Transgenic corn hybrids that express toxins from Bacillus thuringiensis (Bt) are highly effective against the European corn borer, Ostrinia nubilalis (Hübner), and the closely related Asian corn borer, Ostrinia furnacalis (Guenée). Since the registration of Bt corn hybrids in the U.S. in 1996, there has been a great deal of information generated on O. nubilalis. However, relatively little information exists for O. furnacalis. To help determine whether the information generated for O. nubilalis can be leveraged for decisions regarding the use of transgenic Bt corn against O. furnacalis, experiments were designed to determine whether the pattern of sensitivity to various Bt Cry1 toxins is similar between the two species. Test insects included laboratory-reared O. furnacalis originating from Malaysia, a Bt-susceptible laboratory colony of O. nubilalis maintained at the University of Nebraska-Lincoln (UNL) and an out-group consisting of the sugarcane borer, Diatraea saccharalis (F.), from Louisiana which represents a different genus from the same family. O. furnacalis and O. nubilalis exhibited a similar pattern of susceptibility to all the Cry1 toxins and were highly susceptible to the range of Bt toxins tested including Cry1Aa, Cry1Ab, Cry1Ac and Cry1F. Both of the Ostrinia species were more tolerant to Cry1Ba compared with D. saccharalis, although sensitivity of O. furnacalis was intermediate and did not differ significantly from that of O. nubilalis and D. saccharalis. D. saccharalis was also susceptible to the range of toxins tested but unlike the two Ostrinia species, was more tolerant to Cry1F and more susceptible to Cry1Ba. These results indicate that both of the Ostrinia corn borer species are similar in sensitivity to the Cry1Aa, Cry1Ab, Cry1Ac, Cry1Ba and Cry1F toxins, thus suggesting shared toxin receptors and mechanisms of toxicity for the two species.     

Evaluation of actinomycete isolates obtained from herbal vermicompost for the biological control of Fusarium wilt of chickpea

A total of 137 actinomycetes cultures, isolated from 25 different herbal vermicomposts, were characterized for their antagonistic potential against Fusarium oxysporum f. sp. ciceri (FOC) by dual-culture assay. Of the isolates, five most promising FOC antagonistic isolates (CAI-24, CAI-121, CAI-127, KAI-32 and KAI-90) were characterized for the production of siderophore, cellulase, protease, hydrocyanic acid (HCN), indole acetic acid (IAA) and antagonistic potential against Rhizoctonia bataticola, which causes dry root rot in chickpea (three strains viz. RB-6, RB-24 and RB-115) and sorghum (one strain). All of the five FOC antagonistic isolates produced siderophore and HCN, four of them (except KAI-90) produced IAA, KAI-32 and KAI-90 produced cellulase and CAI-24 and CAI-127 produced protease. In the dual-culture assay, three of the isolates, CAI-24, KAI-32 and KAI-90, also inhibited all three strains of R. bataticola in chickpea, while two of them (KAI-32 and KAI-90) inhibited the tested strain in sorghum. When the FOC antagonistic isolates were evaluated further for their antagonistic potential in the greenhouse and wilt-sick field conditions on chickpea, 45-76% and 4-19% reduction of disease incidence were observed, respectively compared to the control. The sequences of 16S rDNA gene of the isolates CAI-24, CAI-121, CAI-127, KAI-32 and KAI-90 were matched with Streptomyces tsusimaensis, Streptomyces caviscabies, Streptomyces setonii, Streptomyces africanus and an identified species of Streptomyces, respectively using the BLAST searching. This study indicated that the selected actinomycete isolates have the potential for biological control of Fusarium wilt disease in chickpea.     

Effects of after-ripening and storage regimens on seed-germination behavior of seven species of Physaria

The after-ripening response has been well documented in many plant species but studies of this topic are lacking in many new oilseed crops such as Physaria. In a factorial experiment, we tested the effect of different after-ripening periods and germination conditions on freshly harvested seeds of seven Physaria species, Physaria argyraea, Physaria fendleri, Physaria gracilis, Physaria rectipes, Physaria recurvata, Physaria sessilis, and Physaria thamnophila. The seeds were stored for 4 and 12 weeks over two saturated salt solutions (LiCl and MgCl₂) to equilibrate seed moisture at three storage temperatures (5, 25, and 35 °C). We likewise tested a dormancy-breaking protocol on these species by using conditions previously recommended for use in genebanks for P. fendleri. The germination tests were conducted with light (1052 lux) and gibberellic acid (GA₃) (100 ppm) and without them. Results suggested that conditions previously set for P. fendleri are also adequate for P. gracilis, P. recurvata, and P. sessilis, but may still be not optimal for the perennial species, P. argyraea, P. thamnophila, and P. rectipes. Overall, higher germination percentages were obtained with light and GA₃ treatments. In all species, we observed slight differences between total germination results after 4 weeks and 12 weeks of storage, with higher values evident only in P. fendleri, P. recurvata, and P. thamnophila after their fresh seeds were subjected to 12 weeks of after-ripening at warm temperatures.     

Antifungal activity of leaf extracts from South African trees against plant pathogens

The antifungal activity of acetone, methanol, hexane and dichloromethane leaf extracts of six plant species (Bucida buceras, Breonadia salicina, Harpephyllum caffrum, Olinia ventosa, Vangueria infausta and Xylotheca kraussiana) were evaluated for antifungal activity against seven plant pathogenic fungal species (Aspergillus niger, Aspergillus parasiticus, Colletotricum gloeosporioides, Penicillium janthinellum, Penicillium expansum, Trichoderma harzianum and Fusarium oxysporum). These plant species were selected from 600 evaluated inter alia, against two animal fungal pathogens. All plant extracts were active against the selected plant pathogenic fungi. Of the six plant species, B. buceras had the best antifungal activity against four of the fungi, with minimum inhibitory concentration (MIC) values as low as 0.02 mg/ml and 0.08 mg/ml against P. expansum, P. janthinellum, T. harzianum and F. oxysporum. Some of the plant extracts had moderate to low activity against other fungi, indicating that the activity is not based on a general metabolic toxicity. P. janthinellum, T. harzianum and F. oxysporum were the most sensitive fungal species, with a mean MIC of 0.28 mg/ml, while the remaining four fungi were more resistant to the extracts tested, with mean MICs above 1 mg/ml. The number of active compounds in the plant extracts was determined using bioautography with the listed plant pathogens. No active compounds were observed in some plant extracts with good antifungal activity as a mixture against the fungal plant pathogens, indicating possible synergism between the separated metabolites, B. salicina and O. ventosa were the most promising plant species, with at least three antifungal compounds. Leaf extracts of different plant species using different methods (acetone, hexane, DCM and methanol) had antifungal compounds with the same R_f values. The same compounds may be responsible for activity in extracts of different plant species. Based on the antifungal activity, crude plant extracts may be a cost effective way of protecting crops against fungal pathogens. Because plant extracts contain several antifungal compounds, the development of resistant pathogens may be delayed.     

Comparative overwintering host range of three Adelphocoris species (Hemiptera: Miridae) in northern China

In northern China, Adelphocoris suturalis, Adelphocoris lineolatus and Adelphocoris fasciaticollis (Hemiptera: Miridae) are common pests of cotton and several other crops. These species have vastly diverse geographic distribution, seasonal dynamics and abundance, the underlying causal factors of which are poorly understood. In this study, the importance of a broad range of plant species as overwintering hosts for each Adelphocoris sp. was compared. Nymphal emergence from a total of 126 plant species was monitored at two distinct locations. The eggs of A. suturalis successfully eclosed from un-plowed cotton field soil and 115 plant species, primarily pastures, weeds and agricultural crops. The eggs of A. lineolatus successfully eclosed from 40 plant species, mainly pastures and weeds. Finally, A. fasciaticollis overwintered on 35 plant species, primarily tree species, weeds and agricultural crops. In conclusion, the most common and widely distributed mirid species, A. suturalis, overwintered on a comparatively broader range of plants compared to the other two species. These observations help to understand the differences in geographical distribution and abundance of the three Adelphocoris species, and constitute the basis for forecasting and pest management protocols for Adelphocoris spp. in China.     

A comparison of monitoring systems used for Ceratitis species (Diptera: Tephritidae) in South Africa

For 16 years a bucket-type trap known as the Sensus fruit fly trap has been used to monitor three fruit fly pest species Ceratitis capitata, Ceratitis rosa and Ceratitis cosyra in South African fruit industries. The relative efficiencies of lures sold for monitoring fruit flies with the Sensus trap in South Africa were determined in field experiments where laboratory-reared C. capitata, C. rosa and C. cosyra were released in a mango orchard within a few metres of Sensus traps containing either Capilure (trimedlure or tert-butyl 4 (or 5) -chloro-2-methylcyclohexane carboxylate), Ceratitislure (protein hydrolysate plus β-caryophyllene) or Questlure (protein hydrolysate plus plant extracts). When using 12-day-old flies, Capilure caught 3 times more C. capitata males than C. rosa males and this difference was more extreme when 3-day-old flies were released. Ceratitislure caught significantly more 12-day-old C. cosyra males than 12-day-old C. capitata males, but the difference was reversed when 3-day-old flies were compared. Questlure showed the least differences between species and age but recovered the lowest proportion of released species. Further comparisons were conducted in an orchard with wild flies using other known attractants in larger yellow Probodelt bucket traps. Capilure caught more male C. capitata than BioLure Fruit Fly 3-component, but BioLure 2-component (trimethylamine and ammonium acetate) was more effective than Questlure for C. capitata females. The 3-component lure was also more effective than both Capilure and Questlure for male and female C. rosa, respectively. Ceratitislure was the most effective lure for male C. cosyra flies and BioLure 3-component was more effective than Ceratitislure and Questlure for female C. cosyra flies. The intervention threshold of 4 flies/trap/week previously used in citrus with Capilure for C. rosa was lowered to 2 C. rosa/trap/week when using the Sensus trap due to the lower sensitivity of this trap-lure combination found for C. rosa in this study. The 3-component lure, or the 2-component combination of trimethylamine and ammonium acetate in a ratio of 1:8 in the Sensus trap capsule, would be more effective for both sexes of all three Ceratitis species than the Questlure that is currently being used.